linux-kernel - Re: [PATCH] rcu-tasks: Fix compilation warning with !CONFIG_TASKS_RCU and CONFIG_TINY

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Date:   Tue, 25 Aug 2020 09:16:29 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rcu-tasks: Fix compilation warning with
 !CONFIG_TASKS_RCU and CONFIG_TINY_RCU

On Tue, Aug 25, 2020 at 06:22:49PM +0300, Laurent Pinchart wrote:
> Hi Paul,
> 
> On Tue, Aug 25, 2020 at 08:02:22AM -0700, Paul E. McKenney wrote:
> > On Sun, Aug 23, 2020 at 06:04:05AM +0300, Laurent Pinchart wrote:
> > > Commit 8344496e8b49 ("rcu-tasks: Conditionally compile
> > > show_rcu_tasks_gp_kthreads()") introduced conditional compilation of
> > > several functions, but forgot one occurrence of
> > > show_rcu_tasks_classic_gp_kthread() that causes the compiler to warn of
> > > an unused static function. Fix it.
> > > 
> > > Fixes: 8344496e8b49 ("rcu-tasks: Conditionally compile show_rcu_tasks_gp_kthreads()")
> > > Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> > > ---
> > >  kernel/rcu/tasks.h | 2 ++
> > >  1 file changed, 2 insertions(+)
> > > 
> > > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> > > index 835e2df8590a..bddf3968c1eb 100644
> > > --- a/kernel/rcu/tasks.h
> > > +++ b/kernel/rcu/tasks.h
> > > @@ -590,7 +590,9 @@ void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
> > >  }
> > >  
> > >  #else /* #ifdef CONFIG_TASKS_RCU */
> > > +#ifndef CONFIG_TINY_RCU
> > >  static void show_rcu_tasks_classic_gp_kthread(void) { }
> > > +#endif /* #ifndef CONFIG_TINY_RCU */
> > >  void exit_tasks_rcu_start(void) { }
> > >  void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
> > >  #endif /* #else #ifdef CONFIG_TASKS_RCU */
> > 
> > Good catch!!!
> > 
> > But does the following addition of "static inline" work for you?
> 
> They do. I initially added a static inline, and realized #ifdef was used
> extensively when trying to find the proper Fixes: tag, so I went for
> that. I don't mind either way, as long as this gets fixed :-)

This is admittedly an odd .h file, given that it is included but once.

I have applied the following patch with your Reported-by, cc-ing -stable
for v5.8 and later.

							Thanx, Paul

> > ------------------------------------------------------------------------
> > 
> > diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
> > index 835e2df..3dc3ffc 100644
> > --- a/kernel/rcu/tasks.h
> > +++ b/kernel/rcu/tasks.h
> > @@ -590,9 +590,9 @@ void exit_tasks_rcu_finish(void) __releases(&tasks_rcu_exit_srcu)
> >  }
> >  
> >  #else /* #ifdef CONFIG_TASKS_RCU */
> > -static void show_rcu_tasks_classic_gp_kthread(void) { }
> > -void exit_tasks_rcu_start(void) { }
> > -void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
> > +static inline void show_rcu_tasks_classic_gp_kthread(void) { }
> > +static inline void exit_tasks_rcu_start(void) { }
> > +static inline void exit_tasks_rcu_finish(void) { exit_tasks_rcu_finish_trace(current); }
> >  #endif /* #else #ifdef CONFIG_TASKS_RCU */
> >  
> >  #ifdef CONFIG_TASKS_RUDE_RCU
> 
> -- 
> Regards,
> 
> Laurent Pinchart